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Asked: 2026-05-28T17:51:58+00:00

Possible Duplicate: !function(){ }() vs (function(){ })() So I was just reading through the

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Possible Duplicate:
!function(){ }() vs (function(){ })()

So I was just reading through the source of the new Bootstrap (2.0) from Twitter and noticed that there is an exclamation mark before the self-invoking anonymous function. When I saw this I immediately thought “Oh crap, there’s a new, better way to do this?”.

See for yourself!

Anyways, what’s the difference? There must be a reason for it because they use it consistently in all of their JavaScript plugins (for Bootstrap).

Another thing I noticed was the “use strict” right after this. I don’t think it’s related to my previous inquiry, but can anyone explain this?

Thanks!

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1 Answer

  1. Editorial Team
    function(){} ();

    By itself (see Point’s comment) isn’t going to be valid, since

    function() {}

    is a function declaration. To invoke it immediately, you need to get the JavaScript engine to treat the function as an expression. People usually do this as either of

    (function(){}) ();  //more common

(function(){} ()); // Papa Crockford's preference:

    with

    !function(){}();

    simply being a shorthand version of the same thing.

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